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Dielectric constant engineering of nonfullerene acceptors enables a record fill factor of 83.58% and a high efficiency of 20.80% in organic solar cells

Journal Article · · Energy & Environmental Science
DOI:https://doi.org/10.1039/d5ee00101c· OSTI ID:2588521
 [1];  [1];  [2];  [1];  [1];  [3];  [1]
  1. Sichuan Univ., Chengdu (China)
  2. Chengdu University of Technology (China)
  3. Brookhaven National Laboratory (BNL), Upton, NY (United States). National Synchrotron Light Source II (NSLS-II)
+ Show Author Affiliations
Organic solar cells (OSCs) have achieved power conversion efficiencies (PCEs) surpassing 20%, but their development remains hindered by the inherently low dielectric constant (εr) of organic semiconductors, which limits charge transport and contributes to serious recombination losses. Herein, we present a comprehensive strategy to overcome the challenge by engineering the dielectric properties of nonfullerene acceptors (NFAs). Two Y-series NFAs of BTP-N3F and BTP-C3F have been synthesized featuring trifluoromethyl (CF3) end-capped alkyl side chains. This molecular design significantly enhances the dipole moment and εr (up to ∼5.9) when compared to the reference acceptor Y6 (∼3), reducing the exciton binding energy (Eb) and improving charge transport. Furthermore, the incorporation of a high-εr polymer additive, poly(pentafluorostyrene) (PPFS), synergistically improves the active layer morphology and dielectric properties, enabling efficient charge extraction and reduced recombination losses. Devices based on the optimized D18-Cl/BTP-C3F system have achieved a record-high fill factor (FF) of 83.58% and an impressive PCE of 20.80%, setting a new benchmark for OSCs. Finally, our results underscore the pivotal role of εr in enhancing device performance and establish a versatile pathway for advancing OSC efficiency and stability through molecular and morphological optimization.
Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Organization:
National Key Research and Development Program of China; National Natural Science Foundation of China; Natural Science Foundation of Sichuan Province; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)
Grant/Contract Number:
SC0012704
OSTI ID:
2588521
Report Number(s):
BNL--228915-2025-JAAM
Journal Information:
Energy & Environmental Science, Journal Name: Energy & Environmental Science Journal Issue: 10 Vol. 18; ISSN 1754-5706; ISSN 1754-5692
Publisher:
Royal Society of Chemistry (RSC)Copyright Statement
Country of Publication:
United States
Language:
English

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36 MATERIALS SCIENCE